The invention is in the field of control and relates to a converter for speed control, particularly for drive systems with electric motors.
In speed control for motor drives, such as are conventionally used e.g. in the storage of signals of suitable carrier or storage materials and the reproduction of these signals, e.g. video signals, acoustic signals, etc., drives are now required having an extremely high constancy of the angular speed. This applies more particularly to all analog recording methods in which the pitch of the reproduced signal is dependent on the instantaneous speed of the record support. Thus, according to the frequency modulation process, the attainable useful/interfering signal ratio is directly dependent on the mechanical constancy of the tape speed in the case of analog data stores.
It is still conventional practice to obtain the requisite running constancy of the drives by suitable flywheel masses which, together with the limited torque capacity of the drive motor, have the effect of a mechanical low-pass filter. In this way, brief disturbances to the drive, as well as load cycle effects, are reduced to assist in bringing about a uniform angular speed. Nevertheless, speed stabilization with the aid of flywheel masses suffers from important disadvantages. Apart from the necessary weight, and the resulting large bearing loads, the stored kinetic energy of the flywheel mass opposes any desired speed change by a very slow modification behaviour.
Thus, it is necessary to avoid this disadvantage wherever the speed is to be constantly, but rapidly, variable.
One known application in this direction is "electronic editing", in which the control of individual drives in complex compound systems takes place by computer. Frequently, equipment for recording and reproducing acoustic and/or video signals are used in such complex compound systems, i.e., equipment which is in part required to have an extremely high running constancy. However, using a computer is very expensive.